Finished initial abstraction of ELF-loader (works for DS)

svn-id: r51233

1 files changed, 143 insertions, 0 deletions

diff --git a/backends/plugins/ds/ds-loader.cpp b/backends/plugins/ds/ds-loader.cpp
new file mode 100644
index 0000000000..7dd27cfb4a
--- /dev/null
+++ b/backends/plugins/ds/ds-loader.cpp
@@ -0,0 +1,143 @@
+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * $URL$
+ * $Id$
+ *
+ */
+
+#include "backends/fs/ds/ds-fs.h"
+#include "../elf-loader.h"
+#include "dsmain.h"
+
+#define __DEBUG_PLUGINS__
+
+#ifdef __DEBUG_PLUGINS__
+#define DBG(x,...) consolePrintf(x, ## __VA_ARGS__)
+#else
+#define DBG(x,...)
+#endif
+
+#define seterror(x,...) consolePrintf(x, ## __VA_ARGS__)
+
+/**
+ * Flushes the data cache.
+ */
+void flushDataCache() {
+  DC_FlushAll();
+}
+
+/**
+ * Follow the instruction of a relocation section.
+ *
+ * @param DLFile 	 SeekableReadStream of File
+ * @param offset 	 Offset into the File
+ * @param size   	 Size of relocation section
+ *
+ */
+bool dlRelocate(Common::SeekableReadStream* DLFile, unsigned long offset, unsigned long size, void *relSegment) {
+	Elf32_Rel *rel = NULL; //relocation entry
+
+	// Allocate memory for relocation table
+	if (!(rel = (Elf32_Rel *)malloc(size))) {
+		seterror("Out of memory.");
+		return false;
+	}
+
+	// Read in our relocation table
+	if (DLFile->seek(offset, SEEK_SET) < 0 ||
+	        DLFile->read(rel, size) != (ssize_t)size) {
+		seterror("Relocation table load failed.");
+		free(rel);
+		return false;
+	}
+
+	// Treat each relocation entry. Loop over all of them
+	int cnt = size / sizeof(*rel);
+
+	DBG("Loaded relocation table. %d entries. base address=%p\n", cnt, relSegment);
+
+	int a = 0;
+	unsigned int relocation = 0;
+
+	// Loop over relocation entries
+	for (int i = 0; i < cnt; i++) {
+
+		// Get the symbol this relocation entry is referring to
+		Elf32_Sym *sym = (Elf32_Sym *)(_symtab) + (REL_INDEX(rel[i].r_info));
+
+		// Get the target instruction in the code
+		unsigned int *target = (unsigned int *)((char *)relSegment + rel[i].r_offset);
+
+		unsigned int origTarget = *target;	//Save for debugging
+
+		// Act differently based on the type of relocation
+		switch (REL_TYPE(rel[i].r_info)) {
+
+		case R_ARM_ABS32:
+			if (sym->st_shndx < SHN_LOPROC) {			// Only shift for plugin section.
+				a = *target;							// Get full 32 bits of addend
+				relocation = a + (Elf32_Addr)_segment;			   // Shift by main offset
+
+				*target = relocation;
+
+				DBG("R_ARM_ABS32: i=%d, a=%x, origTarget=%x, target=%x\n", i, a, origTarget, *target);
+			}
+			break;
+
+		case R_ARM_THM_CALL:
+			DBG("R_ARM_THM_CALL: PC-relative jump, ld takes care of necessary relocation work for us.\n");
+			break;
+
+		case R_ARM_CALL:
+			DBG("R_ARM_CALL: PC-relative jump, ld takes care of necessary relocation work for us.\n");
+			break;
+
+		case R_ARM_JUMP24:
+			DBG("R_ARM_JUMP24: PC-relative jump, ld takes care of all relocation work for us.\n");
+			break;
+
+		case R_ARM_TARGET1:
+			if (sym->st_shndx < SHN_LOPROC) {			// Only shift for plugin section.
+				a = *target;							// Get full 32 bits of addend
+				relocation = a + (Elf32_Addr)_segment;			   // Shift by main offset
+
+				*target = relocation;
+
+				DBG("R_ARM_TARGET1: i=%d, a=%x, origTarget=%x, target=%x\n", i, a, origTarget, *target);
+				DBG("Make sure --target1-abs is a flag to LD.\n");
+			}
+			break;
+
+		case R_ARM_V4BX:
+			DBG("R_ARM_V4BX: No relocation calculation necessary.\n");
+			break;
+
+		default:
+			seterror("Unknown relocation type %d.", REL_TYPE(rel[i].r_info));
+			free(rel);
+			return false;
+		}
+
+	}
+
+	free(rel);
+	return true;
+}